1. Technical Field
Generally, the invention relates to a chair. Particularly, the invention relates to a split back chair having a three-piece back which flexes to wrap around and cradle an occupant's back from side to side and which flexes toward and away from a seat member of the chair. Specifically the invention relates to a split back chair having a generally L-shaped seat member with a vertical section which forms a base of the back, and right and left back portions hingedly connected to the vertical section of the seat member and hingedly connected together.
2. Background Information
Many chairs have been designed which take ergonomic considerations into account. These chairs are designed to support the occupant's spine in an optimum fashion. A number of designs have already been proposed with this goal in mind. Some of these chairs involve a complex and correspondingly expensive mechanism. Others are not only so designed that adjusting them is a complicated process, with the result that the advantages they offer cannot fully be utilized, but are also fitted with superfluous parts making the chair too heavy to use. A chair designed in accordance with ergonomic principles must include means capable of adapting to the movements and the anatomy of the human body so that the occupant can work at optimum efficiency over long periods. Thus, difficulties of the kind outlined above have a negative rather than a positive effect. A correctly designed chair seat embraces and supports the body up to the pelvis in order to allow the trunk to move as freely as possible. When the occupant of the chair remains seated for a prolonged period of time, the natural position of the spine should be maintained.
Examples of chairs which support an occupant's back and spine are shown in U.S. Pat. No. 4,007,962 which discloses a chair with an adjustable back. The chair includes a central section hingedly attached to the rear of the seat, as well as an upper portion flexibly mounted to the top of the center section and extending around both sides thereof.
U.S. Pat. No. 4,157,203 discloses an articulated double back for chairs. The device provides an upper and lower section having a flexible hinge extending intermediate the upper and lower section to provide independent movement therebetween.
U.S. Pat. No. 4,585,272 discloses a chair having a back comprising a plurality of articulated segments. The chair has a reclineable backrest formed by a series of at least three superimposed segments articulated together about respective horizontal axes. The device is moveable to correspond to the arched back of the occupant.
U.S. Pat. No. 4,830,430 discloses a split back chair having a pair of springs formed of two U-bent spring rods which couple a lower back portion of the chair to an upper back portion of the chair. The effective spring length of the springs is adjustable or changeable by moving a slider connected to one of said back portions.
U.S. Pat. No. 5,195,804 discloses a backrest having two oval-shaped shells each concave to vertical and convex to horizontal. The backrest includes two backrest shells arranged at the sides and configured in a manner of contact surfaces of equestrian saddles.
U.S. Pat. No. 5,249,839 discloses a split back chair with independent control of a lumbar portion of a seat back and a thoracic portion of the seat back. The chair has a seat connected to a base and a control connected to the base under the seat. A first support is pivotally connected with the control and extends from the control to the thoracic portion of the seat back. A second support is pivotally connected with the control and extends from the control to the lumbar portion of the seat back. The two supports operate independently and the thoracic and lumbar portions of the seat back rotate independently rearward with respect to the seat.
U.S. Pat. No. 5,385,388 is a continuation-in-part of the '839 patent and is similar thereto having a second support extending to the lumbar portion of the seat back.
Although these prior art devices were adequate for the purpose for which they were intended, some of these chairs include backs which merely pivot toward and away from the seat member allowing the occupant to recline in the forward and backward direction. These chairs fail to disclose a split back having separate right and left portions hingedly interconnected to assure that movement of one of the right and left portions cause movement of the other of the right and left portions through a flexible interconnection. Other of these prior art chairs disclose a split back chair which requires highly mechanical components which facilitate a right and left flexing movement. These chairs are heavy and tend to be expensive to purchase due to the large number of parts associated with the chair.
Therefore, the need exists for a split back chair which has a simplified design and which includes a generally L-shaped seat member and separate right and left back portions hingedly interconnected and hingedly connected to the seat member.